Field of the Invention
The present invention relates to a stencil for forming surface structures by etching, a method for producing such a stencil, a printing machine for producing such a stencil as well as a method for forming surface structures by etching.
Description of Related Art
Stencils known from the prior art for forming surface structures by etching comprise an etch-resistant stencil layer, wherein the stencil layer can be transferred, for example by rubbing, to the surface to be structured and wherein, after an etching treatment of the surface to be structured, the stencil layer can be at least partially removed.
Such stencils are used to produce a structured image, for example the reproduction of a textured leather surface, on metal surfaces, in particular surfaces of injection moulded tools, which in the subsequent injection moulding is transferred to the surface of the injection moulded plastic part.
For this purpose, an etch-resistant stencil layer—normally from a stencil carrier—is transferred to the metal surface. This is usually carried out by placing the stencil carrier, formed for example as a paper or film, on the surface to be structured and the stencil layer is then transferred from the stencil carrier by rubbing, i.e. by applying pressure to the stencil carrier in the direction of the surface to be structured. This is a procedure that is normally performed manually since the surfaces to be structured usually have a three-dimensional shape that does not allow or at least greatly complicates a mechanical transfer of the stencil layer.
When the stencil layer has been transferred to the surface to be structured, the stencil layer thus now forms an acid-resistant layer that covers specific regions of the surface to be structured. If the work piece, for example the injection mould, is now exposed to an acid bath, the reactivity of the uncovered surface of the work piece thus leads to a removal of material as a result of the oxidation initiated by the acid.
Such surface structures formed by etching techniques are very widespread, since in particular the surface of injection-moulded plastic parts substantially shapes the overall appearance of the end product. The requirements placed on the structural images of surface structures produced by etching techniques therefore increase accordingly. In many cases these can only be satisfied if the etching for forming the surface structures takes place in several stages. In this connection a part of each step is the transfer of a stencil layer to the surface to be structured further (with the second step) and a subsequent further treatment in an acid bath. Together with the requirements placed on the final structural image the requirements on the transfer of the stencil layer in a second or in further steps also become more stringent. The effort and expenditure involved in the normally manually performed transfer of a stencil layer to a surface that is already structured by etching is therefore considerable.
To produce a stencil for forming surface structures by etching it is known to use a method in which an etch-resistant stencil layer is applied to a stencil carrier by means of a dot matrix printer. By using a dot matrix printer, i.e. a printer that generates its printed image by composing individual image points, it is possible in a simple way to produce the stencil layer in almost any arbitrary shape.
Known printing machines for producing a stencil for forming surface structures by etching comprise at least one dot matrix printer head and at least one receptacle for a stencil carrier, in which the dot matrix printer head prints a stencil layer on the stencil carrier. In this connection various materials are used to produce the stencil layer. It is known for example to use UV-curable ink or wax.
As already mentioned methods are known for forming surface structures by etching, in which a stencil layer is transferred from a stencil carrier to the surface to be structured and the surface to be structured undergoes an etching treatment after the stencil layer has been applied.
An object of the present invention is to elaborate and develop the known stencils for forming surface structures by etching, the known methods for producing a stencil for forming surface structures by etching, the known printing machines for producing a stencil for forming surface structures by etching and also the known methods for forming surface structures by etching, in which the formation of complicated, multilayer surface structures involving at least two successive etching treatments is significantly simplified and accelerated.